This study is a multicenter, randomized, parallel, double-blind, placebo- controlled comparison of three dosing regimens of EXOSURF Pediatric versus air. Each dosing regimen consists of two intratracheal doses of EXOSURF Pediatric or air given 12 (+/-1) hours apart to infants with birthweights greater than or equal to 1250 grams and with established Respiratory Distress Syndrome (RDS).